54 TRANSACTIONS OF THE ILLINOIS 



Hence they have projected the theory that fungi are the cause of these diseases, without 

 ever inquiring: whether they may not be the effect of them. I have already stated that 

 the seeds (sporangia) of fungi are everywhere present, to seize upon dead matter, when- 

 ever and wherever it is cast off. It is therefore not necessary that they must be produced 

 in swamps and marshes, and issue from them armed with disease and death. Is it not 

 more probable that disease has been induced, the general health impaired, and the vital, 

 action enfeebled by the exhalations of fermenting, rotting vegetable and animal matter ? 

 And to induce disease, may not dead or effete matter have accumulated in the system ? 

 If so, then we can account for the presence of fungi in the system without a resort to 

 the hypothesis that they proceeded from these swamps and produced the disease. If the 

 fact that the chemist's alembic did not detect a deleterious gas in the atmosphere, is to 

 be taken as conclusive that there is none, shall we not also take the decision of the mi- 

 croscope which declares that at the appearance of disease the fungi have not matured 

 any spores, being yet in incipient immature stages ? 



But, then, what produces disease in these localities? I think the old theory of atmos- 

 pheric vitiation the most plausible. I have said fungoid growth is effected by oxygen- 

 ation. Now these fungi that ferment in stagnant, putrid waters, live by consuming the 

 oxygen. If it is vegetable tissue, or any other organic compound they are decomposing? 

 they also decompose the water to obtain the oxygen, and of course the hydrogen and 

 the carbon escape as gas, or as it is called, carbureted hydrogen, which we know is dele- 

 terious to health. There may be other combinations, such as sulphureted hydrogen, etc., 

 which are all inimical to man. If the fungus is decomposing matter in the atmosphere, 

 carbonic acid and other eqmally obnoxious gases are evolved. 



But the question is, are plants injuriously affected by these exhalations ? We cannot 

 say that they are, but we know that in vitiated air, as in close rooms or in dense shades, 

 a fungus soon develops on the foliage. Analogy then leads us to study not only the 

 physiology of plants, but their pathology also. However, at present, this would lead us 

 too far from our purpose. I will therefore close by giving you a theory of my own 

 respecting the origin of many of the diseases that afflict our plants. 



Starch, and albuminous compounds of metamorphosed starch is the principal element 

 of seeds. Wood producing or plants with perennial woody stems generally grow longi- 

 tudinally the first year only until the stores of starch in the cotyledon are exhausted ; 

 that is they grow until they are organized with stem and leaves, and then grow laterally 

 (thicken) by layers of woody fiber.* But this is not all, in the fall and winter this 

 woody fiber is well stored with starch. At the end of the season of longitudinal growth 

 analysis of the wood shows that the starch is exhausted. The starch has been consumed 

 in pushing forward skeleton stems and making the parenchyma of the leaves. In other 

 words it has been consumed in organizing the plant to enable it to perform its annual 

 work. We Avill now suppose that the pruning knife, disease, or accident when so organ- 

 ized deprive it of so much foliage that it cannot work up the nutriment thrown into the 

 leaves by the roots. Its store of last year's material is exhausted, it therefore makes a 

 draft upon the stores preparing for the next. But the new material is in an immature 

 condition. The plant, however, is in a desperate strait and must have it. It therefore 

 makes use of it, such as it is. The second growth of all plants and trees is made in this 



*The peach is almost the only exception to this statement. It, howoever, also comes to a halt 

 when the seed leaves of the cotyledon are exhausted, bid soon starts again, and continues grow- 

 ing, both longitudinally and latteraly until the close ot the season. 



